The lignin degradation system (LDS) of Phanerochaete chrysosporium has been implicated in the degradation of lignin and a variety of environmental pollutants that are hazardous to human health. The LDS is a multicomponent system that includes lignin peroxidases, manganese peroxidases and glucose 1-oxidase. My long term goals are to understand the genetic regulation of the LDS, to delineate the role of the LDS in the degradation of organic compounds, and to develop an ability to manipulate and regulate the expression of the genes involved in the degradative processes. A collection of genetically pure mutants of LDS, two auxotrophic mutants and wild type variants of the ME446 strain, are available for genetic studies. The mutants of LDS appear to be regulatory in nature and are missing one or more components of LDS. Specific objectives of the proposed research are to genetically analyze these mutants by crosses, to determine whether the level of control is at the transcriptional level by northern blot analysis, and to study gene interaction by heterokaryon analysis. The purpose of these experiments is to gain an understanding of the genetic regulation. Isolation of additional mutants of primary metabolism and of the LDS by X-ray mutagenesis is also proposed. Biochemical characterization of selected wild type variants will be performed in order to understand the heterogeneity of the wild type strain ME446. In addition, mutants missing various components of LDS will be utilized to delineate the role of these components in the degradation of a model organic compound. Proposed studies are expected to enhance our understanding of the genetic regulation of the LDS and provide well characterized mutants for the isolation of regulatory genes in future.